CVE-2026-53396 (GCVE-0-2026-53396)
Vulnerability from cvelistv5
Published
2026-07-19 12:01
Modified
2026-08-17 04:50
Severity ?
7.1 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: nfsd: fix posix_acl leak and ignored error in nfsd4_create_file nfsd4_create_file() has two bugs in its ACL handling: The return value of nfsd4_acl_to_attr() is silently discarded. When the NFSv4-to-POSIX ACL conversion fails (e.g., -EINVAL for unsupported ACE types), the file is created without any ACL and the client receives NFS4_OK. This violates RFC 7530/8881 which require the server to reject unsupported attributes on CREATE. When start_creating() fails after ACL attributes have been populated in attrs (either via nfsd4_acl_to_attr or via ownership transfer from open->op_dpacl/op_pacl), the function jumps to out_write which skips nfsd_attrs_free(). The posix_acl allocations are leaked. A client can trigger this repeatedly with OPEN(CREATE), ACL attributes, and an invalid filename (e.g., longer than NAME_MAX). Fix both by capturing the nfsd4_acl_to_attr() return value and by changing the early error paths to jump to out instead of out_write. Initialize child to ERR_PTR(-EINVAL) so that end_creating() is safe to call even if start_creating() was never reached.
References
Impacted products
Vendor Product Version
Linux Linux Version: 7ab96df840e60eb933abfe65fc5fe44e72f16dc0
Version: 7ab96df840e60eb933abfe65fc5fe44e72f16dc0
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "18cf006a08babec0bbac2a3784f8f28e56e47490",
              "status": "affected",
              "version": "7ab96df840e60eb933abfe65fc5fe44e72f16dc0",
              "versionType": "git"
            },
            {
              "lessThan": "24c975bbdd564d7d0ad90294bfa69729830345de",
              "status": "affected",
              "version": "7ab96df840e60eb933abfe65fc5fe44e72f16dc0",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/nfsd/nfs4proc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.19"
            },
            {
              "lessThan": "6.19",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.3",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.3",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "6.19",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnfsd: fix posix_acl leak and ignored error in nfsd4_create_file\n\nnfsd4_create_file() has two bugs in its ACL handling:\n\nThe return value of nfsd4_acl_to_attr() is silently discarded.  When\nthe NFSv4-to-POSIX ACL conversion fails (e.g., -EINVAL for\nunsupported ACE types), the file is created without any ACL and the\nclient receives NFS4_OK.  This violates RFC 7530/8881 which require\nthe server to reject unsupported attributes on CREATE.\n\nWhen start_creating() fails after ACL attributes have been populated\nin attrs (either via nfsd4_acl_to_attr or via ownership transfer from\nopen-\u003eop_dpacl/op_pacl), the function jumps to out_write which skips\nnfsd_attrs_free().  The posix_acl allocations are leaked.  A client\ncan trigger this repeatedly with OPEN(CREATE), ACL attributes, and an\ninvalid filename (e.g., longer than NAME_MAX).\n\nFix both by capturing the nfsd4_acl_to_attr() return value and by\nchanging the early error paths to jump to out instead of out_write.\nInitialize child to ERR_PTR(-EINVAL) so that end_creating() is safe\nto call even if start_creating() was never reached."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The vulnerable code is reached via NFSv4 OPEN(CREATE) handled by nfsd over the network (RPC on TCP/2049), from nfsd4_proc_compound() through nfsd4_open() and do_open_lookup() into nfsd4_create_file().\nAC:L - An authenticated NFS client can reliably trigger the leak by sending OPEN(CREATE) with ACL attributes and a filename that causes start_creating() to fail (e.g., longer than the backing filesystem NAME_MAX); no race or attacker-uncontrollable conditions are required.\nPR:L - Exploitation requires an authenticated NFS client with write/create permission on the target export directory (enforced by fh_verify()/nfsd_permission), which maps to basic authorized-user access rather than unauthenticated or server-admin privileges.\nUI:N - No victim interaction is needed beyond the attacker sending crafted NFSv4 compound requests to the server.\nS:U - Impact is confined to kernel memory management and exported file metadata within the NFS server\u0027s security authority; it does not cross VM, container, or IOMMU boundaries.\nC:N - The bug is a refcount leak of posix_acl kernel objects with no out-of-bounds read, use-after-free, or other mechanism that exposes kernel memory to the attacker.\nI:L - The ignored nfsd4_acl_to_attr() error allows files to be created without the requested ACL while returning NFS4_OK, causing limited but incorrect modification of exported file security attributes on shared storage.\nA:H - Repeated triggering leaks unbounded posix_acl slab objects per request, enabling sustained kernel memory exhaustion that can deny NFS service and degrade overall system availability."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T04:50:48.148Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/18cf006a08babec0bbac2a3784f8f28e56e47490"
        },
        {
          "url": "https://git.kernel.org/stable/c/24c975bbdd564d7d0ad90294bfa69729830345de"
        }
      ],
      "title": "nfsd: fix posix_acl leak and ignored error in nfsd4_create_file",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-53396",
    "datePublished": "2026-07-19T12:01:58.375Z",
    "dateReserved": "2026-06-09T07:44:35.402Z",
    "dateUpdated": "2026-08-17T04:50:48.148Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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